在從MySQL遷移到Postgres後，瞭解「SEPARATOR」處或附近的語法錯誤

Question

我最近不得不徹底改造最初使用MySQL的Django項目，但爲了部署到Heroku（根據他們的建議docs regarding Django deployment），我遷移了通過以下方法MySQL數據庫的Postgres：

1. 安裝依賴關係：pyscopg2和py-mysql2pgsql

2. 設置Postgres數據庫

3. 個遷移數據庫：$ py-mysql2pgsql - 這將創建一個mysql2pgsql.yml文件，它看起來像這樣：

   mysql: hostname: localhost port: 3306 socket: /tmp/mysql.sock username: foo password: bar database: your_database_name compress: false destination: postgres: hostname: localhost port: 5432 username: foo password: bar database: your_database_name

4. 通過傳輸的數據：$ py-mysql2pgsql -v -f mysql2pgsql.yml

的咖啡許多杯之後，部署Heroku成功了（大部分情況下，直到我今天發現這個問題），該應用程序按照預期在heroku上運行，並運行$ heroku local。但今天，在前端訪問某個功能時，與數據庫中的錯誤在瀏覽器中出現：

DatabaseError at /projects/ 

syntax error at or near "SEPARATOR" 
LINE 1: ...s, sc.name as sport_category, string_agg(au.email SEPARATOR ... 
                  ^

Request Method:  GET 
Request URL: http://0.0.0.0:8989/projects/ 
Django Version:  1.5.1 
Exception Type:  DatabaseError 
Exception Value:  

syntax error at or near "SEPARATOR" 
LINE 1: ...s, sc.name as sport_category, string_agg(au.email SEPARATOR ... 

我相信相關的代碼是在一個名爲business.py：

def getAllProjects(self): 
     ''' 
     @note: Retrieve all projects 
     ''' 

     from django.db import connection 
     cursor = connection.cursor() 

     cursor.execute("select p.id, p.title, p.description, p.deadline, pt.name as project_type, s.name as status, sc.name as sport_category, group_concat(au.email SEPARATOR '\n') as project_managers from project p left join project_manager_in_project pmip on p.id = pmip.project_id left join auth_user au on pmip.project_manager_id = au.id inner join project_type pt on p.projectType_id = pt.id inner join status s on p.status_id = s.id inner join sport_category sc on p.sportCategory_id = sc.id where p.deleted = 0 group by p.id") 
     projects = cursor.fetchall() 
     return projects 

我知道，談論類似問題的幾個帖子：

Postgresql - concat_ws like function?

Postgresql GROUP_CONCAT equivalent?

這導致我試圖將group_concat(au.email SEPARATOR '\n')更改爲string_agg(au.email SEPARATOR '\n')，然後array_agg(au.email SEPARATOR '\n')但我仍然收到相同的錯誤。

是否有另一種方法我應該這樣做，並調整此功能以實現解決方法？

UPDATE：任何人誰是有興趣的，所提供的選擇的答案（和評論）考慮我下面把我帶到下面改變查詢語句這沒有問題迄今的工作原理：

cursor.execute("select \"project\".\"id\", project.title, project.description, \"project\".\"deadline\", \"pt\".\"name\" as \"project_type\", \"sc\".\"name\" as status, \"sc\".\"name\" as sport_category, string_agg(au.email, E'\n') as project_managers from project left join project_manager_in_project pmip on project.id = pmip.project_id left join auth_user au on pmip.project_manager_id = au.id inner join project_type pt on project.\"projectType_id\" = pt.id inner join status s on project.\"status_id\" = \"s\".id inner join sport_category sc on \"project\".\"sportCategory_id\" = \"sc\".\"id\" where project.deleted = 0 group by 1,2,3,4,5,6,7") 

由於這個應用程序的原始開發人員已創建所有的雙引號表，這導致了column p.projecttype_id does not exist錯誤和其他類似的does not exist錯誤，當我所做的一切都被刪除SEPARATOR和group_concat（兩者都不存在於Postgres）至string_agg。換句話說，根據考慮我的建議，我不得不使用雙引號封裝幾乎所有的表名和列名（並且當然要避免使用引號）。

Answer 1

正如您已經看到您需要用STRING_AGG()替換GROUP_CONCAT()。在GROUP BY子句中包含聚合函數中未使用的每一列。

select 
    p.id, 
    p.title, 
    p.description, 
    p.deadline, 
    pt.name as project_type, 
    s.name as status, 
    sc.name as sport_category, 
    string_agg(au.email, E'\n') as project_managers 
from 
    project p 
    left join project_manager_in_project pmip on p.id = pmip.project_id 
    left join auth_user au on pmip.project_manager_id = au.id 
    inner join project_type pt on p.projectType_id = pt.id 
    inner join status s on p.status_id = s.id 
    inner join sport_category sc on p.sportCategory_id = sc.id 
where 
    p.deleted = 0 
group by 1,2,3,4,5,6,7 

Postgres中沒有SEPARATOR關鍵字（至少我不知道它的存在）。